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Jupiter
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Jupiter
Pronunciation
i/'d?u?p?t?r/
Adjective
Jovian
Epoch J2000
Aphelion
816,520,800 km (5.458104 AU)
Perihelion
740,573,600 km (4.950429 AU)
Semi-major axis
778,547,200 km (5.204267 AU)
Eccentricity
0.048775
Orbital period
4,332.59 days
11.8618 yr
10,475.8 Jupiter solar days
Synodic period
398.88 days
Average orbital speed
13.07 km/s
Mean anomaly
18.818°
Inclination
1.305° to Ecliptic
6.09° to Sun's equator
0.32° to Invariable plane
Longitude of ascending node
100.492°
Argument of perihelion
275.066°
Satellites
64
Mean radius
69,911 ± 6 km
Equatorial radius
71,492 ± 4 km
11.209 Earths
Polar radius
66,854 ± 10 km
10.517 Earths
Flattening
0.06487 ± 0.00015
Surface area
6.1419×1010 km2
121.9 Earths
Volume
1.4313×1015 km3
1321.3 Earths
Mass
1.8986×1027 kg
317.8 Earths
1/1047 Sun
Mean density
1.326 g/cm3
Equatorial surface gravity
24.79 m/s2
2.528 g
Escape velocity
59.5 km/s
Sidereal rotation
period
9.925 h (9 h 55 m 30 s)
Equatorial rotation velocity
12.6 km/s
45,300 km/h
Axial tilt
3.13°
North pole right ascension
268.057°
17 h 52 min 14 s
North pole declination
64.496°
Albedo
0.343 (Bond)
0.52 (geom.)
Surface temp.
1 bar level
0.1 bar
min
mean
max
165 K
112 K
Apparent magnitude
-1.6 to -2.94
Angular diameter
29.8" — 50.1"
Surface pressure
20–200 kPa (cloud layer)
Scale height
27 km
Composition
89.8±2.0%
hydrogen (H2)
10.2±2.0%
helium
~0.3%
methane
~0.026%
ammonia
~0.003%
hydrogen deuteride (HD)
0.0006%
ethane
0.0004%
water
Ices:
ammonia
water
ammonium hydrosulfide(NH4SH)
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian or outer planets.The planet was known by astronomers of ancient times and was associated with the mythology and religious beliefs of many cultures. The Romans named the planet after the Roman god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of -2.94, making it on average the third-brightest object in the night sky after the Moon and Venus. (Mars can briefly match Jupiter's brightness at certain points in its orbit.)Jupiter is primarily composed of hydrogen with a quarter of its mass being helium; it may also have a rocky core of heavier elements. Because of its rapid rotation, Jupiter's shape is that of an oblate spheroid (it possesses a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding the planet is a faint planetary ring system and a powerful magnetosphere. There are also at least 64 moons, including the four large moons called the Galilean moons that were first discovered by Galileo Galilei in 1610. Ganymede, the largest of these moons, has a diameter greater than that of the planet Mercury.Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. The most recent probe to visit Jupiter was the Pluto-bound New Horizons spacecraft in late February 2007. The probe used the gravity from Jupiter to increase its speed. Future targets for exploration in the Jovian system include the possible ice-covered liquid ocean on the moon Europa.
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